Apparatus and process for refining paper stock



Feb. 18, 1969 D. w. DANFORTH APPARATUS AND PROCESS FOR REFINING PAPERSTOCK Filed May 4. 1966 INVENTOR Donald W. Dcmforrh PW fpewmv ATTORNEYSUnited States Patent 8 Claims ABSTRACT OF THE DISCLOSURE A truncated,conical type paper refiner is provided with plug fillings or shelllinings in which the working face is pitted with a multiplicity of smalldiameter holes, the sum of the hole area being equal to, or greaterthan, the sum of the non-hole area and the ratio of the hole edge lengthto the area of the face associated with each hole comprises apredetermined ratio consisting a K factor of from about 3.6 to about3.8.

This invention relates to paper stock engines of the type having afrusto-conical plug revolvable in a frustoconical shell such as Jordanengines and Claflin engines. More particularly the invention relates toimproved comminuting surfaces or tackle for such englnes.

Such engines have opposed shell fillings and plug linings, each withirregularly surfaced comminuting members such as bars, knives, or thelike, which provide, in addition to a shearing action, whereby fiberbundles are beaten apart or refined, a cutting action. It has formerlybeen proposed to modify the meeting surfaces of these fillings orlinings with hydration-producing holes wherein such holes cover an areanot exceeding one-half of the entire surface. This proposal was embodiedin US. Patent No. 1,583,771 to Bidwell of May 11, 1926, and has beensuccessfully utilized in the art of paper making for many years.However, it has always been desirable to improve the performance of thistype of apparatus both in respect to the uniform quality of productwhich could be obtained therefrom and with respect to the operatingcosts required by the apparatus.

Therefore, it is a principal object of the instant invention to providean improved paper refiner of the Jordan or Claflin type.

It is a further object of the invention to provide apparatus that willbe capable of processing an improved paper stock.

It is another object of the inventionto provide apparatus that iscapable of producing high quality paper stock at reduced operatingcosts. a

It is still another object of the invention to provide a paper stockrefiner with a comminuting surface having holes therein of such size andspacing that the refining action of the apparatus is improved.

Another object of the invention is to provide an improved process formaking paper stock.

Still another object of the invention is to provide an improvedreplaceable comminution surface for paper refiners.

Applicant has substantially met the above objects with the surprisingdiscovery that the performance of the type of comminuting surfacepreviously known to the art as described in the Bidwell patent can begreatly improved by spacing and sizing the holes on a comminuting sur-.face in such a way as to maintain an appropriate ratio of hole-edgeperimeter to non-hole surface area of the working surface relativelyconstant but to increase the ratio of hole area to non-hole surface areato well in 3,428,262 Patented Feb. 18, 1969 ice excess of 1:1, thelimitation taught by the prior art. Thus, a particularly advantageousembodiment of the invention could utilize a stationary shell workingsurface have inch holes on a inch center-to-center spacing arrangement.Such a shell would have a ratio of hole area to non-hole surface area ofabout 1.4 to 1. However, shells having ratios of hole area to non-holearea of up to 2 and more are also useful and within the scope of theinvention. Moreover, the advantages of the apparatus of the inventionare particularly evident when the ratio of total hole edge length toassociated non-hole surface area is between 3.6 and 3.8 mostadvantageously about 3.7. This term will be referred to henceforth as aK factor and is, where holes are laid out on equilateral triangles, afunction of the hole diameter and distance between hole centers:

In this application and accompanying drawings, I have shown anddescribed a preferred embodiment of my invention and have suggestedvarious alternatives and modifications thereof, but it is to beunderstood that these are not intended to be exhaustive and that otherchanges and modifications can be made within the scope of the invention.These suggestions herein are selected and included for purposes ofillustration in order that others skilled in the art will more fullyunderstand the invention and the principles thereof and will be enabledto modify it and embody it in a variety of forms, each as may be bestsuited to the condition of a particular case.

FIGURE 1 is an elevational view, partially in section, of the refiningsection of a refining engine of the Claflin type.

FIGURE 2. is a plan view of a segment of a stationary hydrating elementaccording to the invention.

FIGURE 3 is an enlarged, side view in half section, on line 3-3 of FIG.4 of one of the hydrating segments of the invention.

FIGURE 4 is a section through line 4-4 of FIG- URE 2.

FIGURE 5 is a fragmentary diagrammatic plan view showing the preferreddiameter and spacing of the holes of the invention on a greatly enlargedscale.

Referring now to FIGURE 1, it is seen that refining apparatus 12includes a truncated conical plug mounted on a shaft 14 journalled ateach end in bearings 16 and 18. The outer shell 20, of apparatus 12,comprises a stock inlet 22 and a stock outlet 24. These outlets areconnected by a conical flow path 26 through which pulp being refined ispassed.

On the inner surface of shell 20. is a stationary filling 28 having acomminuting surface 29 thereon. Opposing the filling 28 is the pluglining 30 mounted on plug 32, which plug is, in turn, mounted on shaft14.

Plug lining 30 is equipped with bars, or knives, 33 on the surfacethereof, such as are known in the art to provide good refining action.

In operation, as will be understood by those skilled in thepaper-manufacturing art, plug lining 30 is rotated at such speeds as toexert a high shear on the fibrous material carried between the shell andplug members 28 and 30 in fiow path 26.

FIGURES 2 and 3 show a segment 40 of stationary shell filling 28. Thefilling 28 is assembled by mounting a series, such as sixteen, ofsegments 40 within shell 20. Each segment 40 is cast, in one piece, incastable metal, such as steel. A large number of holes 42, each indiameter and centered apart one from another, are cast into the smooth,comminuting, or working surface 44 of segment 40. The extremities 43 ofeach segment 40 are machined for fit into shell 20 as is known in theart.

FIGURE 4 shows an end view of segment 40 more clearly showing theconcave shapes required for fitting of the arcuate segments 40 withinshell 20. Also shown in FIGURE 4 are cross-sections of some of the holes42 in comminuting surface 44. The holes shown are one inch in depth, andspaced uniformly about 7 apart. There are preferably about 700 to 800holes 42 in each segment, but this, of course, depends on the size ofthe machine and number of segments required therefor.

It has been found that one of the most critical and significant factorsresponsible for good performance characteristics in pitted, orperforated, hydrating shell designs is the ratio of effective edgelength to exposed surface area. Thus, as the hole size is increased, thedistance between holes should be increased accordingly to maintain thiscritical ratio of edge to area.

As shown diagrammatically in FIGURE 5, the centres of the holes can belocated at the apices of equilateral triangles with sides of length D.With this arrangement, the area associated with each hole is hexagonalin shape. The exposed surface area per hole (which is believed toaccomplish the essential brushing of the fibres), can be defined as thearea of the hexagon AH minus the area of the hole itself AO. Similarlythe length of effective edge per hole (which is believed to accomplishthe cutting or shearing of the fibres) can be defined as half thecircumference projected on the plane of the axis, or simply diameter d.

Utilizing the dimensions of a particular known hydrating shell of theBidwell type having drilled holes, for example in diameter and betweenhole centres, a constant K can be developed representing the ratio ofedge to area, as follows:

Area of hexagon=AH=0.865D

Area of hole=AO=0.785d

Surface area associated with each hole=AH-AO; Projected length of edgeof each hole=d;

or when d=% and D=% K=3.5

Ratio of edge to area=K= Distance Hole Between K Diameter Centers ofFactor Holes Drilled Hole Type %2 2 3. 5 Cast Hole Type 1...- ie %2 3. 7Cast Hole Type II 94s %2 3. 7 Cast Hole Type III M6 %2 3. 7

Apparatus made essentially according to the illustrated embodiment ofthe invention, having holes /8 in diameter, with between centres, wastested in a Clafiin type refiner rated for handling one to three tons ofstock per hour. In control tests, hydrating members, constructedaccording to the teachings of Bidwell and having holes 7 inch indiameter with about between centres were utilized on the outercomminution surface, i.e., the stationary shell filling of the sameengine. Each testedapparatus had conventional bar-type members on therotating surface.

Three comparisons of per-formance were made with the two machines usingthe following conditions:

Experimenl 1.The horsepower was maintained constant and the throughputwas varied.

Experiment 2.The throughput was maintained constant and the horsepowerwas varied.

Experiment 3.--Throughput and horsepower were both allowed to vary andthe freeness of feedstock (called furnish in the art) was held constant.

In each instance, the performance of the apparatus of the instantinvention was superior.

Especially noticeable was the improved minimum properties of paper madefrom the pulp refined in applicants apparatus. Table I below shows acomparison of the values of paper quality as measured by variouswellknown control tests. The three papers A, B and C were carefullyprepared in the same manner from identical stock excepting A wasprepared from a non-refined control, B was prepared from paper refinedin the abovementioned Bidwell-type apparatus, and C was prepared inapparatus according to the instant invention.

RESULTS AS PERCENT OF A A B B C C It is abundantly clear that theapparatus of the instant invention performed extremely well especiallyin respect to the uniform good quality of the paper produced from thepulp refined therein as evidenced by the relatively high minimumstrength characteristics and improved maximum strength characteristics.

Moreover, in Experiment 2, the instant apparatus operated at aconsiderable power saving while achieving the same output.

In Experiment 3, performance of the novel apparatus as measured by thefiber length retention and production of fewer tfines was also clearlysuperior to the performance of the Bidwell-type apparatus.

The apparatus of the instant invention may be constructed of any of thematerials known to the art to be advantageous in pulp-processingoperations. For example, chrome-manganese or other stainless steels,mild steel, manganese, and the like.

The size of the holes may be varied somewhat. For example, holes of frominch to inch and larger may be used if they are spaced sufiiciently farapart to permit a proper hole area: non-hole area ratio and desirable Kfactor. For example, to maintain the ratio shown for the illustrativeembodiment described above, the following preferred table may begenerally followed for engineering convenience:

Of course, it is understood that the rows of holes are staggered in amanner such as that suggested in the drawings.

The shape of the cast holes may be other than round, and, indeed, exceptfor the added expense of forming such holes, in some applications othershapes, for example, polygons or ellipses, are often highly advantageousinasmuch as they increase the ratio of hole-edge to surface area andthus increase the cutting capacity of the apparatus. The depth of theholes may also vary. Normally they are rather deep in order toprecompensate for expected wear. Usually they perform best when A; inchor more deep. Another variable factor is the shape of the hole. It isusually most convenient depending on the method of manufacture used, tohave the holes taper slightly toward the bottom. When the taper issmall, the

effect of tackle wear on change in hole dimension or refiner performanceis not important. 7

It is also to be emphasized that the novel pitted comminution surfaceswhich have been described above may be utilized on either or both of thetreatment surfaces in paper refining apparatus. For example, the plugmay have a novel surface such as that described herein, or the innersurface of the shell may have such a. surface, or both shell and plugmay have novel surfaces according to the invention. Furthermore, thenovel cornminuting surface described herein may make up only a portionof the total surface of the stationary or rotating surfaces. Choice ofwhich, or how many such surfaces will be embodied in the apparatus ofthe invention, is largely dependent on the type of refining actiondesired to be imparted to the pulp by the tackle during its passagethrough the refining apparatus.

What is claimed is:

1. In a stock engine of the type having a frustoconical plug revolvablewithin a frusto-conical shell wherein said plug and said shell havecomminuting members with irregular faces thereon,

the improvement comprising at least one said comtminuting member havinga plurality of holes in the face thereof but wherein the ratio of thesum crosssection of said holes to remaining face area is greater than 1to 1, and the K factor of said comminuting member is from about 3.6 toabout 3.8.

2. An engine as defined in claim 1, wherein said ratio of the sumcross-section of said holes to remaining face area is at least about1.15, wherein said holes are equallyspaced one from another, and said Kfactor is from about 3.6 to 3.8.

3. An engine as defined in claim 2 wherein said holes are from aboutinch to 7 inch in diameter, and said K factor is from about 3.6 to 3.8.

4. An engine as defined in claim 3 wherein one said comminuting surfacecomprises a series of bars thereon.

5. A replaceable structure adaptable for mounting on, and dismountingfrom, a stock engine of the type having a frusto-conical shell,

said structure comprising a comminuting surface having a plurality ofsmall diameter holes, the ratio of total cross-sectional area of suchholes to the remaining face area of said surface being greater than 1 to1 and the K factor of said surface being about 3.7.

6. In a process for refining pulp stock, by subjecting said stock to amechanical shearing action between two comminuting surfaces, theimprovement comprising subjecting said stock to cutting and brushingaction by at least one said surface which is provided with a pluralityof small diameter holes, the sum cross- 6 sectional area of which holesis greater than the remaining area on said comminuting surface and the Kfactor of which surface is about 3.7, thereby subjecting said stock toexcellent cutting and brushing action while simultaneously minimizingthe mechanical energy dissipated in heating said pulp stock.

7. A cast unitary filling segment for the shell of a truncated, conicalrefining engine, said segment comprising a generally triangular body ofcast material having a concave, arcuate, relatively smooth, planar innerworking face,

and a multiplicity of evenly spaced, cored holes cast in the material ofsaid body, each generally normal to said face, each about three-eighthsof an inch in diameter, and each converging slightly from said innerface toward the outer face of said body,

the total sectional area of all of said holes in said face being atleast equal to the area of the remainder of said working face betweensaid holes, and the K factor of said working face being from about 3.6to about 3.8.

8. A stock refining engine of the type having opposed, relativelymovable, stock treatment faces,

at least one said face comprising a plurality of identical detachablesegments, each said segment being a unitary body of cast metal having asmooth working face pitted with holes therein and extending over theentire face thereof, said holes being of predetermined diameter andspaced apart a predetermined distance in a uniform pattern,

the cross-sectional area of the holes in each said segment being atleast equal to the area of the remainder of the working face of saidsegment,

and said working face having a predetermined ratio of projected lengthof edge of each hole to surface area associated with each hole, saidratio constituting a K factor of about 3.7.

References Cited UNITED STATES PATENTS W. GRAYDON ABERCROMBIE, PrimaryExaminer.

US. Cl. X.R. 241-260, 294

